What happens to my Steem dollars?

What happens to my Steem dollars?
I'm just new to Steemit, I have put a few Videos on , but i dont really understand it yet.
One thing i was wondering was, where do the Steem dollars go? You can put them in to savings but then what happens?
I would be greatful if anyone could shed a little light on this.

The other question is? How are the Steem dollars generated , where do they come from? after all there are no adverts so how does it generate an income ?

thanks for anyone who replies